Like other manufacturing disciplines, well drilling technology has been integrated with electronics for measurements, computing, communications, etc. As well drilling capabilities have allowed drilling of deeper wells, the temperature of the well fluid, otherwise known as “mud” has increased to the point where insulation and/or cooling of the downhole electronics is required to keep the electronics operational. Attempts have been made to insulate the electronics but even if a truly adiabatic insulator was available, the heat generated by the electronics themselves would lead to overheating if a cooling mechanism was not incorporated into the design of the electronics system.
Attempts have been made to provide a coolant to the electronic systems but the depth of state of the art wells has made this task difficult. Typical wells can be many thousands of feet deep and can include bends in the well that make plumbing one or more coolant lines to the drill head difficult. Further, existing methods of chaining multiple measurement and data collection downhole tools together in a single well further complicates an already difficult task of cooling individual tools and their associated electronic components. Further, attempts have been made to insulate the electronic components from the heat associated with the external environment but these attempts have resulted in a fixed operational time based on the amount of time required for the heat source to overcome the insulator, combined with heat generated by the electronics, and raise the temperature of the electronic components to a temperature at which they cannot operate.
Many prior art systems and mechanisms have evolved to transfer heat from a higher temperature region to a lower temperature region or to perform mechanical work based on the aforementioned energy transfer. One such device for performing mechanical work based on the described temperature difference is a Stirling engine. A Stirling engine is a device that converts thermal energy into mechanical energy by exploiting a difference in temperature between two regions.
The Stirling engine operates on the principle of the Stirling cycle which consists of four thermodynamic processes acting on a working fluid. The Stirling cycle consists of an isothermal expansion, an isovolumetric cooling, an isothermal compression and a isovolumetric heating. The output of the Stirling cycle is the ability to perform mechanical work based on movement of the piston in the Stirling engine. Noteworthy in the theory of the Stirling cycle is the reversible nature of the Stirling cycle. Accordingly it is possible to provide the mechanical energy to the Stirling engine and create a heat exchanger capable of transferring heat from a region of lower temperature to a region of higher temperature.
Accordingly, it would be desirable to provide devices and methods that avoid the afore-described problems and drawbacks of cooling downhole electronics.